1. Field of the Invention
The present invention relates to a portable terminal, and more particularly to a portable terminal in which noise induced into an antenna can be reduced, so as to improve the reception performance of the antenna, and in particular, an antenna of a portable terminal implementing a Long Term Evolution (LTE) service.
2. Description of the Related Art
As a high-quality multimedia service is provided together with a voice communication service through a portable terminal for mobile communication, a wireless communication technology is getting a lot of attention due to the convergence of itself with a next-generation wireless communication service such as LTE.
In order to smoothly receive a multimedia service provided by such a wireless communication technology, a rate for transmitting huge amounts of multimedia data at high speed must be guaranteed. Therefore, research on an antenna of a portable terminal suitable for a high-speed data transmission rate has been continuously conducted.
Typically, a voice communication service-based communication system using a Single-Input Single-Output (SISO) system, uses only a single antenna element that mainly has narrow-band channel characteristics in a limited frequency domain. However, a SISO system using such a single antenna has many difficulties when transmitting large amounts of data at high speed in a narrow-band channel.
Therefore, there has been a need for a Multiple-Input Multiple-Output (MIMO) technology which is a next-generation wireless transmission technology by which each antenna of a plurality of antennas can be independently driven and data can be transmitted at a higher data transmission/reception rate with a lower error probability. These MIMO antennas have an advantage in that limited frequency resources can be efficiently used by using multiple antennas at a transmission/reception end of the communication system.
The conventional technology of these MIMO antennas is disclosed in Korean Patent Laid-Open Publication No. 10-2010-0113938 (Publication Date: Oct. 22, 2010, Title of the Invention: Broad-band MIMO (Multi-Input Multi-Output) Antennas), Korean Patent Registration No. 10-0932420 (Registration Date: Dec. 9, 2009, Title of the Invention: MIMO Antenna System), etc.
However, these MIMO antennas which are installed in a limited space of a portable terminal, raise a problem in that high interference between the antennas is caused by an electromagnetic wave emitted between the antennas. The MIMO antennas installed in the portable terminal are arranged at positions, which are physically as far apart from each other as possible in the portable terminal.
Recently, in a bar-shaped portable terminal which implements an LTE system, a primary transmission/reception antenna among the MIMO antennas is located at a lower end of the portable terminal, and a diversity reception antenna among the MIMO antennas is located at an upper end of the portable terminal.
However, due to the characteristics of the bar-shaped portable terminal, elements including a motor (such as typically used to generate a vibration as a “call alert”), an earphone jack, a camera, a sensor, etc. are arranged near the diversity reception antenna. These elements generate various noises including an electromagnetic wave. When a frequency band of these noises overlaps (or duplicates) the reception frequency band of the diversity reception antenna, noises generated by the elements are induced into the antenna, so that problems occur in that not only is the reception strength of the antenna reduced, but the performance of the antenna is also reduced.
Even furthermore, the reduced reception strength and performance of the antenna causes a problem in that the reliability of a portable terminal in an LTE system is reduced because the LTE system has to transmit/receive data at high speed with a low error probability.